Cable terminal for high voltage cables

ABSTRACT

A circuit device electrically connects a bus bar to a high voltage cable core of a cable terminal. The cable terminal has an insulating body for supporting the cable core relative to ground. A voltage transformer is structurally combined with the cable terminal and has a dielectric comprising part of the insulating body of the cable terminal.

United States Patent [191 Kessler et al.

54] CABLE TERMINAL FOR HIGH VOLTAGE CABLES [75] Inventors: ClausKessler; Werner Kohler, both of Berlin, Germany [73] Assignee: SiemensAktiengesellschalt, Berlin and Munich, Germany [22] Filed: Sept. 8, 1970[21] Appl. No.: 70,047

[52] U.S. Cl. ..324/96, 174/73, 174/139 [51] Int. Cl ..G0lr 31/00, H02g3/00, HOld 17/00 [58] Field of Search ...324/96; 174/73 R, 73 SC, 139,

[5 6] References Cited UNITED STATES PATENTS I 3,450,827 6/1969 Phillips174/73 [451 Jan. 9, 1973 1,981,716 11/1934 Austin ..174/139x 1,775,5299/1930 .lansson ..174/139x Primary Examiner-Alfred E. SmithAlt0rney-Curt M. Avery, Arthur W. Wilfond, Herbert L. Lerner and DanielJ. Tick [57] ABSTRACT A circuit device electrically connects a bus barto a high voltage cable core of a cable terminal. The cable terminal hasan insulating body for supporting the cable core relative to ground. Avoltage transformer is structurally combined with the cable terminal andhas a dielectric comprising part of the insulating body of the cableterminal.

9 Claims, 3 Drawing Figures SHEET 1 [IF 3 FIG.

CABLE TERMINAL FOR HIGH VOLTAGE CABLES DESCRIPTION OF THE INVENTION Theinvention relates to a high voltage switch cell. More particularly, theinvention relates to a high voltage switch cell having a bus bar, avoltage transformer and a circuit device for electrically connecting thebus bar to the cable vcore of a cable terminal. The cable terminal hasan insulating body for supporting the cable provide a An object of theinvention is to provide a high voltage switch cell which is economicalin production and operation.

An object of the invention is to provide a high voltage switch cellwhich functions with efficiency, effectiveness and reliability.

In accordance with the invention, a high voltage switch cell comprises acable terminal for a cable having a high voltage cable core. A circuitdevice electrically connects a bus bar to the cable terminal. The cableterminal has an insulating body for supporting the cable core of thecable relative to ground. A voltage transformer is structurally combinedwith the cable ter minal and has a dielectric comprising part of theinsulatin g body of the cable terminal.

The voltage transformer is a capacitive voltage transformer having apair of electrodes covering different parts of the surface of theinsulating body of the cable terminal.

The insulating body of the cable terminal is a tube having a centerregion which is the dielectric of the voltage transformer. One endencloses the high voltage conductor and another end encloses the cablecore of the cable and supports the cable core in electrical contact witha high voltage conductor.

A cover on the insulating body of the cable terminal at the other endthereof seals the insulating body at the other end and tightly clampsthe cable.

A current transformer is mounted on the other of the insulating body ofthe cable terminal.

A plug contact in the insulating body of the cable terminal electricallyconnects the cable core of the cable to the high voltage conductor. 1

The cable has a ground conductor and the cable is clamped by the coverof the insulating body at a ground contact of the ground conductor ofthe cable.

Electrically conducting means electrically conducts the measured valueof the current transformer to indicating means and optically conductingmeans optically conducts the measured value of the voltage transformerto the indicating means.

The voltage transformer is a capacitive voltage transend former having apair of electrodes covering different 2 produced by the semiconductorbody to the indicating means.

The insulating body of the cable terminal thus functions as thedielectric of the voltage transformer in the high voltage switch cell ofthe invention, and the voltage transformer is structurally combined withthe cable terminal. The separately produced and separately assembledconventional cable terminals and transformers are thus replaced by thecircuit device of the invention which may be manufactured as a unit andwhich may be replaced and inserted as a unit. The structural combinationmay be further enhanced by providing ground potential at the side ofsaid combination which is farther from the free end of the cableterminal, since in such region the shielding and armor of the cable areto be connected to ground. From a dielectric point of view, this largelyprovides the same conditions as during the measurement of the voltagebetween the high voltage conductor and ground in a transformer. Thisresults in a simplification of the cable entry and a saving of spacewithout additional effort or expense.

The switch cell of the invention is particularly easy to provide withthe voltage transformer comprising a capacitive transformer havingelectrodes which cover parts of the surface of the insulating body ofthe cable terminal. The insulating body of the cable terminal preferablycomprises a cast resin body. The electrodes are provided as conductivelayers coated on the insulating body. Suitable electrically conductinglayers may comprise, for example, a conductive varnish. The cast resinbody determines the shape of the electrodes of the capacitivetransformer.

The insulating body may comprise a laminated body having a plurality oflaminations or sheets of a desired electrode configuration. Thelaminations or sheets may be utilized as formed members in themanufacture of cast resin bodies. The cast resin body is formed by theelectrodes.

As hereinbefore described, the insulating body of the cable tenninalpreferably comprises a tube having a center region which functions asthe dielectric of the voltage transformer. One end of the insulatingtube en closes a high voltage conductor and the other end of the tubeencloses the cable core of the cable terminal, which is in electricalcontact with the high voltage conductor. The insulating tube is ofsubstantially cylindrical configuration and is relatively easy toproduce. If necessary, the insulating tube may be sealed and, undercertain circumstances, may be filled with a high valency dielectric of atype usually utilized with cable terminals. The switch cell of theinvention is most preferable for synthetic cables having cable terminalswhich do not require a liquid or gaseous dielectric.

Additional simplification is provided by mounting a current transformeron the end of the insulating body parts of the surface of the insulatingbody of the cable terminal. One of the electrodes is on the ground sideof the voltage transformer. A semiconductor body of lumines'centmaterial is on the one of the electrodes. A photocell is in the area ofindicating means. Light conducting means conducts the voltage-dependentlight which encloses the cable core of the cable terminal. The devicethereby provided thus functions to determine, at one locality, allmeasured quantities for con- I trolling the high voltage switch cell.The cable core of the cable terminal functions as the primary conductorof the current transformer.

As hereinbefore described, the cable core of the cable terminal may beelectrically connected to the high voltage conductor via a plug contact.This con- I siderably facilitates the assembly of the cable terminal.

The insulating body may then be readily removed at the end enclosing thecable core of'the cable terminal, afier the high voltage conductor isdisconnected, to free the cable. The device may be assembled byreinserting the .soldered on said cable, for example, for absorbing thecontact forces necessary for current transmission.

As hereinbefore described, the end of the insulating body enclosing thecable terminal may be provided with a cover which seals said insulatingbody and tightly clamps the cable terminal. The tight clamping of thecable terminal prevents the cable from being disconnected from the plugcontact when high current forces prevail. The clamping area may also beprovided as a ground contact for the ground conductor of the cable. In ahigh current switch cell, two parallel connected cables may be clampedby the cover at the end of the in sulating tube. The two cables togetherprovide the necessary electrically conductive cross-sectional area andare affixed to each other by theinsulating body.

As hereinbefore described, the measurand or measured value of thecurrent transformer may be conducted to an indicator by electrical meansand the measurand or measured value of the voltage transformer may beconducted to the indicator by optical means. This eliminates theinfluence of the considerably higher secondary currents of the currenttransformer on the very small currents of the voltage transformer. Theelectrode of the capacitive voltage transformer, on the ground side,is'preferably provided with a semiconductor body comprising luminescentmaterial. The voltagedependent light produced by the semiconductor bodyis then conducted by a light conductor to a photocell in the area of theindicator. The luminescent material may be sprayed onto the insulatingbody, or upon a resistance material applied to the insulating body, sothat said luminescent material is between the ground side electrode ofthe capacitive voltage transformer and a As shown in the sectional viewof the bus bar 4, each of the bus bars has a flat copper conductoraffixed thereto. Each of the flat copper conductors 10 is bent atsubstantially right angles, with oneleg of the right angle affixed tothe corresponding bus bar by any suitable means such as, for example,bolts, and with the other leg functioning as the stationary part of aplug connection. The bus bar 2 has a plug connection 11 The bus bar 3has a plug connection 12. The bus bar 4 has a plug connection 13. I

A power switch has connecting leads 14 which are connected to the busbars 2, 3 and 4 via the plug connections 11, 12 and 13, respectively.The power switch 15 is affixed to a driving or operating housing viasupport insulators 17 and 18. The housing 20 is supported by av carriage22. The carriage 22 has wheels 23 and 24 which roll on a moving bottom25 of the housing 1. v

A cable terminal 27 is positioned below the bus bars 2, 3 and 4. A flatcopper conductor 29, bent at right angle, extends from the cableterminal 27. The copper conductor 29 functions as the stationary part ofa plug connection 30 for a connecting lead 33 of the power switch 15.The plug connection 30 includes a pair of flat copper bus bars 34 whichare bent at angles so that they are spaced at a greater distance fromeach other at each end thereof. The bus bars 34 remain substantiallyparallel to each other throughout most of their length. The ends 35 ofthe bus bars 34 are thus bent away from each other and elastically pressagainst the flat copper conductor 29.

Two control electrodes 37 and 38 are affixed to the flat-conductor 29and facilitate the closing of the plug connection. The controlelectrodes 37 and 38 also function to .make the electric field moreuniform so that part at ground potential such as, for example, afastening flange of the insulating body.

In order that the invention may be readily carried into effect, it willnow be described with reference to the accompanying drawings, wherein:

' FIG. I is a schematic diagram, partly in section,'of an embodiment ofthehigh voltage switch cell of the invention; and

FIG. 2 is a cutaway view, partly in section, of an em bodiment of thecircuit device of the invention;

FIG. 3 is a view, similar to FIG. 2, showing some details of theindicating means.

In the Figs., the same components are indicated by the same referencenumerals. I

In FIG. 1, the high voltage switch cell, which may operate at 20kilovolts, for example, is housed in a,

metal housing 1. The housing 1 may comprise sheet metal. Three bus bars2, 3 and 4 are positioned in the housing 1. The bus bar 2 is affixed toan intermediate wall 8 by an insulator 5. The bus bar 3 is affixed tothe intermediate wall 8 by an insulator 6. The bus bar 4 is affixed tothe intermediate wall 8 by an insulator 7.

the applied voltage may be maintained with only slight interruptions.

The cable terminal is shown on a considerably enlarged scale in FIG. 2.The left half of the cable terminal in FIG. 2 is shown in cutaway orsectional view. The principal component of the cable terminal 27 is aninsulating body 40. The insulating body 40 preferably comprises castresin of substantially cylindrical shape,

as illustrated. The insulating body 40 encloses the high voltage cablecore 42 of each of a pair of parallel connected high voltage cables 43aand 43b.

The high voltage cables 43a and 43b are enclosed by polyethyleneinsulation. The cables 43a and 43b are enclosed at an end of thecylindrical insulating body 40. At the end of the cylindrical insulatingbody 40 opposite that which encloses thecables 43a and 43b, saidinsulating body has ribs 45 formed on its outer surface. A high voltageconductor 46 is inserted in the end of the insulating body 40 at whichthe ribs 45 are formed. The high voltage conductor 46 extendsfrom itsend of the cylindrical insulating body 40 via a flat copper conductor29. The high voltage conductor 46 is fixed in position by a snap ring 47which engages a groove formed on the inside surface of the insulatingbody 40 at the end thereof which encloses the high voltage conductor 46.

The insulating body 40 has an inside electrode 50 affixed to its inside.surface in the center region of said insulating body and an outsideelectrode 51 affixed to its outside surface in said center region. Theelectrodes 50 lead 55 extends to an appropriate indicating or measuringdevice.

A current transformer 56 is provided at the lower end of the insulatingbody 40. The current transformer 56 is constructed as an attachable ringenclosing a laminated ring core 57 and a low voltage winding 58 seatedon said core. The high voltage winding is the high voltage cable core 42of the cables 43a and 43b. A connecting lead 59 from the low voltagewinding 58 extends into the depression 53 of the insulating body 40.

The lower end of the insulating body 40 is sealed by a I cover 60 ofinsulating material. When the cover 60 is pressed against the currenttransformer 56, a plurality of contact laminations or sheets 61 arespread apart, against the force of an annular or ring spring 62. One end63 of each of the laminations or sheets 61 is in abutment with a groundconductor 64 and the other end 65 of each of said laminations or sheetsis in abutment with a metal cover or armor 66 of the cables 43a and 43b,which armor is grounded. The cables 43a and 43b are thus grounded andtightly clamped by the cover 60.

The insulating body 40 of the cable terminal 27 is surrounded at itscenter region by a lamination, sheet, sleeve, wrapping, or the like, 67which is fastened to said insulating body via two reinforcing ribs 68and 69. A sheet flange 70 is welded to the sleeve 67. The sheet flange70 may be affixed to a metal support member 71 by any suitable meanssuch as, for example, bolts 72a and 72b.

Another sheet, lamination, sleeve, wrapping, or the like, 73 is providedaround the end of the insulating body 40 which encloses the cables 43aand 43b. The sleeve 73 covers the current transformer 56 and permits thecover 60 to be affixed to the insulating body 40. The cover 60 may beinserted into the end of the sleeve 73.

In order to equalize the voltage stress in the insulating body 40, theinside electrode of the capacitive voltage transformer 52 is providedwith a bent end portion 75 which points toward the end of saidinsulating body which encloses the cables 43a and 43b. The bent edgeportion of the inside electrode 50 comprises the same material as theoutside electrode 51. The material of the bent edge portion 75 of theinside electrode 50 and of the outside electrode 51 comprises aconductive layer of epoxide resin varnish having metal powder. Theepoxide resin preferably has the same basic substance as the cast resinof the insulating body 40.

A plug contact 76 provides an electrical connection between the cables43a and 43b and the high voltage conductor 46. The plug contact 76comprises elastic contact laminations or sheets affixed to the highvoltage conductor 46. The cable core 42 of each of the cables 43a and43b engages the plug contact 76 via a clamped or otherwise suitablyaffixed bolt 77. The bolt 77 may be soldered, for example.

In the illustrated embodiment, the measurand or measured value of thevoltage transformer 52 is galvanically transmitted to a measuring orindicating device, as is the measurand or measured value of the currenttransformer 56. Instead of galvanic transmission of the measurands ofthe voltage transformer 52 a layer of resistance material havingluminescent characteristics may be provided on the outside surface ofthe insulating body 40. The luminescent material produces a specificamount of light depending upon the voltage. The light is preferablydirected via a lens system 80 and is transmitted via a light conductor81 to a measuring or indicating device 82, wherein a photocell 83 ispositioned and receives the measured value or measurand. (FIG. 3)

The light conductor 81 may comprise a rod of transparent material havingan index of refraction which is higher than that of air and whichconducts the light entering at one end thereof to the other end thereof,almost without loss, and via bends or angles in the rod. The lightemerges from the other end. This type of light conductor permits themeasurand or measured values of the voltage transformer 52, havinglittle or weak energy, to be guided through the relatively high measuredvalues or measurand of the current transformer,

to the measuring or indicating device of the voltage. The measurands maybe shielded at the indicating or measuring device.

FIG. 1 illustrates, in broken lines, a voltage transformer seated on thecarriage 22, and a current transformer affixed to the rear wall of thehousing 1. Such voltage and current transformers are eliminated by theswitch cell of the invention. The space, which would otherwise byutilized by the voltage and current transformers, may thus be utilizedfor other components or may be utilized to reduce the size of the switchcell.

While the invention has been described by means of a specific exampleand in a specific embodiment, we do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention.

We claim:

1. A cable terminal for high voltage cables having high voltage cablecores used in high voltage switch cells, comprising a bus bar, a voltagetransformer structurally combined with the cable terminal, a currenttransformer and a switching device connecting the bus bar to the cableterminal, said cable terminal comprising an insulating body supportingthe cable core relative to ground, the insulating body forming thedielectric for the voltage transformer, indicating means, electricallyconducting means for electrically conducting the measured value of thecurrent transformer to the indicating means, and optically conductingmeans for optically conducting the measured value of the voltagetransformer to the indicating means.

2. A high voltage switch cell as claimed in claim 1,

wherein said voltage transformer is a capacitive voltage transformerhaving a pair of electrodes covering different parts of the surface ofthe insulating body of the cable terminal.

3. A high voltage switch cell as claimed in claim 1, further comprisinga high voltage conductor, and

' further comprising a cover on the insulating body of the cableterminal at the other end thereof sealing said insulating body at saidother end and tightly clamping the cable.

5. A high voltage switch cell as claimed in claim 3,

further comprising a current transformer mounted on the other end of theinsulating body of the cable terminal.

6. A high voltage switch cell as claimed in claim 3,

I furthercomprising a plug contact in the insulating body of the cableterminal for electrically connecting the cable core of the cable to thehigh voltage conductor.

7. A high voltage switch cell as claimed in claim 4, wherein the cablehas a ground conductor and said cable isvclamped by the cover of saidinsulating body at a ground-contact of the ground conductor of saidcable.

8. A high voltage switch cell, comprising a cable terminal fora cablehaving a high voltag cable core;

a bus bar; I

a circuit'device for electrically connecting the bus bar to the cableterminal, said cable terminal hav-' ing an insulating body forsupporting the cable core of the cable relative to ground;

a voltage transformer structurally combined with the cable terminal andhaving a dielectric comprising part of the insulating body of the cableterminal;

a high voltage conductor, the insulating body of the cable terminalbeing a tube-having a center region which is the dielectric of thevoltage transformer, one end enclosing the high voltage conductor andanother end enclosing the cable core of the cable and supporting saidcable core in electrical contact with said high voltage conductor;

a current transformer mounted on the other end of the insulating body ofthe cable terminal; I

indicating means;

electrically conducting means for electrically conducting the measuredvalue of the current transformer to the indicating means; and

optically conducting means for optically conducting the measured valueof the voltage transformer to the indicating means.

9. A high voltage switch cell as claimed in claim 8,

wherein the voltage transformer is a capacitive voltage transformerhaving a pair of electrodes covering different parts of the surface ofthe insulating body of the' cable terminal, one of said electrodes beingon the ground side of said voltage transformer, and further comprising asemiconductor body of luminescent material on said one of saidelectrodes, indicating means, a photocell in the area of said indicatingmeans, and light conducting means for conducting the voltagedependentlight produced by said semiconductor body to said indicating means.

1. A cable terminal for high voltage cables having high voltage cablecores used in high voltage switch cells, comprising a bus bar, a voltagetransformer structurally combined with the cable terminal, a currenttransformer and a switching device connecting the bus bar to the cableterminal, said cable terminal comprising an insulating body supportingthe cable core relative to ground, the insulating body forming thedielectric for the voltage transformer, indicating means, electricallyconducting means for electrically conducting the measured value of thecurrent transformer to the indicating means, and optically conductingmeans for optically conducting the measured value of the voltagetransformer to the indicating means.
 2. A high voltage switch cell asclaimed in claim 1, wherein said voltage transformer is a capacitivevoltage transformer having a pair of electrodes covering different partsof the surface of the insulating body of the cable terminal.
 3. A highvoltage switch cell as claimed in claim 1, further comprising a highvoltage conductor, and wherein the insulating body of the cable terminalis a tube having a center region which is the dielectric of the voltagetransformer, one end enclosing the high voltage conductor and anotherend enclosing the cable core of the cable and supporting said cable corein electrical contact with said high voltage conductor.
 4. A highvoltage switch cell as claimed in claim 3, further comprising a cover onthe insulating body of the cable terminal at the other end thereofsealing said insulating body at said other end and tightly clamping thecable.
 5. A high voltage switch cell as claimed in claim 3, furthercomprising a current transformer mounted on the other end of theinsulating body of the cable terminal.
 6. A high voltage switch cell asclaimed in claim 3, further comprising a plug contact in the insulatingbody of the cable terminal for electrically connecting the cable core ofthe cable to the high voltage conductor.
 7. A high voltage switch cellas claimed in claim 4, wherein the cable has a ground conductor and saidcable is clamped by the cover of said insulating body at a groundcontact of the ground conductor of said cable.
 8. A high voltage switchcell, comprising a cable terminal for a cable having a high voltagecable core; a bus bar; a circuit device for electrically connecting thebus bar to the cable terminal, said cable terminal having an insulatingbody for supporting the cable core of the cable relative to ground; avoltage transformer structurally combined with the cable terminal andhaving a dielectric comprising part of the insulating body of the cableterminal; a high voltage conductor, the insulating body of the cableterminal being a tube having a center region which is the dielectric ofthe voltage transformer, one end enclosing the high voltage conductorand another end enclosing the cable core of the cable and supportingsaid cable core in electrical contact with said high voltage conductor;a current transformer mounted on the other end of the insulating body ofthe cable terminal; indicating means; electrically conducting means forelectrically conducting the measured value of the current transformer tothe indicating means; and optically conducting means for opticallyconducting the measured value of the voltage transformer to theindicating means.
 9. A high voltage switch cell as claimed in claim 8,wherein the voltage transformer is a capacitive voltage transformerhaving a pair of electrodes covering different parts of the surface ofthe insulating body of the cable terminal, one of said electrodes beingon the ground side of said voltage transformer, and further comprising asemiconductor body of luminescent material on said one of saidelectrodes, indicating means, a photocell in the area of said indicatingmeans, and light conducting means for conducting the voltage-dependentlight produced by said semiconductor bodY to said indicating means.